2014 Medal Winners | francais

The 2014 CAP/DCMMP Brockhouse Medal

is awarded to

Ian Affleck

"I feel very honoured that our interdisciplinary research is being recognized by the Brockhouse Medal for advances in condensed matter and materials physics." winner citation

The Canadian Association of Physicists (CAP) is pleased to announce that the 2014 CAP/DCMMP Brockhouse Medal is awarded to Ian Affleck, University of British Columbia, for his original and influential contributions to the theory of condensed matter systems, particularly in the application of conformal field theory techniques to the Kondo effects and quantum impurity problems and advances in the theory of quantum magnetism in low dimensions. announcement

Ian Affleck has been an international leader in developing the theory of strongly correlated systems for over 25 years. He has helped to introduce several important theoretical techniques and concepts into the field while also directly interpreting and inspiring experimental work.

His early work on the theory of high-Tc superconductivity introduced the large-N approximation into the study of the Hubbard model, leading to the prediction of two novel phases with spontaneous orbital currents and bond-centered charge density waves as well as introducing the now-popular concept of effective gauge symmetry.

The Affleck-Kennedy-Lieb-Tasaki (AKLT) models are a set of exactly solvable Hamiltonians for antiferromagnets with Heisenberg symmetry on general lattices in one, two and three dimensions. They have attracted great attention for several reasons. In many cases their ground states are magnetically disordered with an energy gap to all excited states and exponentially decaying spin correlation functions. This both provided a theoretical underpinning to the conjecture that one-dimensional (1D) integer spin Heisenberg antiferromagnets have an energy gap, and gave an early example of a gapped spin liquid phase in 2 and 3 dimensions. In a joint theoretical-experimental paper, Affleck and collaborators showed that the 1D spin-1 AKLT model has gapless spin excitations at the ends of a finite chain, explaining experimental observations on NENP.

Affleck developed a theory for 3D Heisenberg antiferromagnets consisting of weakly coupled chains which predicted an analogue of the Higgs particle, thus explaining puzzling neutron scattering results on CsNiCl3 from Chalk River.

Affleck and collaborators developed a powerful theoretical technique, boundary conformal field theory, to study various types of quantum impurities, quantum dots and quantum junctions in condensed matter physics. One consequence is the Affleck-Ludwig entropy.

Affleck is a fellow of the Royal Society (London) and winner of the 2012 APS Onsager Prize. nominator citation

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